Calabro to present mildew research at cherry symposium


News staff writer

January 20, 2007

Three years after she arrived in the Hood River Valley, researcher Jill Calabro is finishing her doctoral research on powdery mildew in sweet cherries.

On Jan. 25, Calabro will present part of her work at the annual Sweet Cherry Symposium in The Dalles. It will be held at the Columbia Gorge Discovery Center from 8 a.m. to 4 p.m.

Calabro came to the Mid-Columbia Agricultural Research and Extension Center from Wisconsin. She was working at the University of Wisconsin on poplar trees but came to Oregon to switch crops and earn her doctorate in plant pathology.

“I wanted to work with a fruit crop,” she said. “I enjoy fruit pathology.”

She has reached the stage of writing her thesis for her doctoral program through Oregon State University. Her path to this point has taken her to Iowa State University where she earned her Bachelor of Science degree in horticulture and her Master of Science in plant pathology from the University of Minnesota.

Calabro said she went into horticulture after growing up on a corn and soybean farm in western Iowa but not for the reasons people might think.

“I wasn’t allowed to help in the fields with things like detassling, walking the beans,” she said. “Mom wouldn’t even let me ride on the tractor as she said ‘it would mess up my hair.’”

When she was in junior high, a close aunt recruited Calabro’s help with a vegetable booth at the local’s farmers market. Her mom still didn’t want her working in the fields but that changed when Calabro went on to college.

When she began studying horticulture, she got hands-on experience working in the fields and now orchards in the Columbia Gorge. She said cherry growers were instrumental in securing funds for the program. Her advisor, Bob Spotts, of OSU, and Gary Grove, of Washington State University, designed the position and came up with an outline of the research work she would do.

Powdery mildew and subsequent infections are caused by a fungus that attacks the leaves of the tree from the leaf to the fruit. While it doesn’t kill the tree, the mildew does weaken it. Cherries infected by the mildew become unmarketable.

“Packing houses will refuse it,” she said. “For exports, it has a very big impact.”

She said the disease is a problem in certain areas but not others. For example, powdery mildew is not a problem for California growers. In the Gorge, there is even a difference in how severe the disease hits in The Dalles compared to Hood River.

“It prefers a drier climate and is the opposite of a typical plant pathogen,” Calabro said. “It’s very well-adapted to The Dalles and has been a problem for years and years.

The disease is a windborne pathogen. Over the years, there have been pockets of it also develop in the Hood River Valley.

She studied the effect of certain management practices and how that impacted mildew development. Part of that included looking at techniques for pruning and training systems as well as different cultivars.

“To see if there were differences among resistance and susceptibility,” she said.

Part of what she found was a correlation between the increase in powdery mildew and some of the later-bearing cultivars being planted in orchards.

“They are more prone to mildew than the early varieties,” she said. “Sweethearts are very susceptible and so are Lapins.”

She did find Regina-variety cherries to be one of the most resistant types and that she was “very impressed with it in terms of mildew.”

Calabro wanted to thank the many orchardists who helped in her research as well as those who funded the project.

“Without the support of the cherry growers, I wouldn’t be here,” she said.

Between now and April, Calabro will finish her thesis. She would prefer to stay in the area as to moving back to the Midwest but needs to find a job once she has finished her doctoral studies.

“One of my favorite things about this program here at Oregon State with the cherries — and probably the main reason I chose it over others — was the close contact with the growers,” she said. “I really like feeling that I’m doing something that is directly applicable to them.”

She might teach or conduct research or do both depending on where she goes. The Oregon Sweet Cherry Commission and the Washington Tree Fruit Research Commission paid for her research.

Orchardists who helped in her field research included Robin Locke, Mel and Mike Omeg, Jim Reed, the Polehn family, Leonard and Paul Aubert and John Carter.

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